For the purpose of manufacturing a narrow slab such as a material for a thin sheet, a method is known which comprises transversely cutting a wide strand cast in a continuous casting machine at a certain length to prepare a wide slab, and then, longitudinally fusion-cutting said wide slab to manufacture a plurality of narrow slabs. According to this method, it is possible to improve the casting efficiency of a cast strand in a continuous casting machine.
When manufacturing two narrow slabs, a first slab 2 and a second slab 3, by longitudinally fusion-cutting a wide slab 1, as shown in FIG. 1, by the method described above, a cutting burr 4 sticks to the lower surface of the first slab 2, and a cutting burr 5 sticks to the lower surface of the second slab 3.
When rolling the first slab 2 having the cutting burr 4 and the second slab 3 having the cutting burr 5, flaws are produced in the rolled products, resulting in defective products and a lower product yield. It is therefore necessary to fully remove the cutting burr 4 sticking to the lower surface of the first slab 2 and the cutting burr 5 sticking to the lower surface of the second slab 3 before rolling thereof. However, since the removal of the cutting burrs 4 and 5 has so far been manually carried out with the use of a cutter or a hot scarfer handled by an operator, the efficiency has been very low, thus impairing smooth manufacture of slabs.
Japanese Utility Model Provisional Publication No. 60568/81 dated May 23, 1981 (hereinafter referred to as the "prior art") discloses an apparatus for removing a cutting burr sticking to the lower surface of a slab along the fusion-cutting line. The prior art is described below with reference to FIG. 2.
In FIG. 2, 6' is a roller table which comprises a plurality of rollers 6a' and extends horizontally for placing a slab 2' having a cutting burr 4' on the lower surface thereof along the fusion-cutting line with the lower surface down, and transferring the slab 2' thereon. The slab 2' is placed on the roller table 6' with the line of the cutting burr 4' intersecting perpendicularly the travelling direction of the roller table 6'.
In FIG. 2, A' is a burr cutting machine provided below the roller table 6' for removing the cutting burr 4' of the slab 2'. The burr cutting machine A' comprises a cutter carriage 7' horizontally moving toward the line of the cutting burr 4' of the slab 2', a cutter carriage driving mechanism 8' connected to the cutter carriage 7', a horizontal stand 9' for mounting the cutter carriage 7' and the cutter carriage driving mechanism 8', and a stand lifting mechanism 10' fitted to the lower portion of the horizontal stand 9' for lifting the horizontal stand 9' together with the cutter carriage 7' and the cutter carriage driving mechanism 8'. The cutter carriage 7' has at the top thereof at least one cutter 11', and each of the at least one cutter 11' has a knife 11a' for cutting off the cutting burr 4' of the slab 2'. Also in FIG. 2, 12' are a pair of supporting legs vertically provided on a base 13', and an end of the horizontal stand 9' is connected by a shaft 14' to the top portion of the pair of supporting legs 12'. A slab fixing mechanism (not shown) for fixing the slab 2' onto the roller table 6' during cutting off the cutting burr 4' of the slab 2', is provided near the burr cutting machine A'.
The stand lifting mechanism 10' has the following construction. In FIG. 2, 15' is a rack fixed onto the base 13', 16' is a bearing fixed onto the rack 15', and 17' is a shaft inserted horizontally into the bearing 16'. An end of a first arm 18' extending substantially horizontally and an end of a second arm 19' extending substantially vertically are respectively fixed to the shaft 17' so that the first arm 18' and the second arm 19' form an angle of about 90.degree. therebetween. In the same figure, 20' is a bracket fixed onto the base 13', and 21' is a cylinder connected by a shaft 22' substantially horizontally to the bracket 20', the tip of a rod 21a' of the cylinder 21' being connected by a shaft 23' to the other end of the second arm 19'. A jaw member 24' having a jawshaped engaging portion 24a' is fixed to the lower portion of the horizontal stand 9', and a roller 25' fitted to the other end of the first arm 18' is engaged with the jawshaped engaging portion 24a' of the jaw member 24'. Since the stand lifting mechanism 10' has the construction as described above, it is possible to lift the horizontal stand 9' via the first arm 18 and the second arm 19, with the shaft 14' provided at the top of the supporting leg 12' as the fulcrum by causing the rod 21a' to expand through actuation of the cylinder 21', and to lower the horizontal stand 9' by causing the rod 21a' to contract through actuation of the cylinder 21'.
The cutter carriage driving mechanism 8' comprises a cylinder provided substantially horizontally on the upper surface of the horizontal stand 9', and the tip of a rod 8a' of the cylinder is connected by a shaft 26' to the cutter carriage 7' having wheels 7a'. It is therefore possible to forward, the cutter carriage 7' on a rail (not shown) provided on the horizontal stand 9', by causing the rod 8a' to expand through actuation of the cutter carriage driving mechanism 8', and to retreat the cutter carriage 7' by causing the rod 8a' to contract.
In FIG. 2, 27' and 28' are a pair of cutter supporting members fixed onto the top portion of the cutter carriage 7'. Each of the at least one cutter 11' is attached between the pair of cutter supporting members 27' and 28' by means of a shaft 29' inserted into an elliptic hole (not shown) formed in each of the at least one cutter 11' so that each of the at least one cutter 11' can be vertically moved by a distance equal to a play between the elliptic hole and the shaft 29'. In the same figure, 30' is at least one cylinder provided substantially vertically on the top portion of the cutter carriage 7', and the tip of a rod 30a' of the at least one cylinder 30' is in contact with a recess 31' formed at the lower portion of each of the at least one cutter 11'. Therefore, it is possible to vertically move the at least one cutter 11' by a distance equal to a play between the elliptic hole and the shaft 29' by actuating the at least one cylinder 30'.
Now, operation of the above-mentioned apparatus of the prior art is described. A slab 2' placed on the roller table 6' with the lower surface having the cutting burr 4' of the slab 2' down, is fixed onto the roller table 6' by the slab fixing mechanism (not shown). Then, the cutter 11' is brought into contact with the lower surface having the cutting burr 4' of the slab 2' by actuating the stand lifting mechanism 10' of the burr cutting machine A' to lift the horizontal stand 9', and actuating the cylinder 30' on the cutter carriage 7' to lift the cutter 11'. Then, the cutter 11' is horizontally moved, while keeping the contact with the lower surface of the slab 2', toward the line of the cutting burr 4' until the cutter 11' passes the line of the cutting burr 4' by actuating the cutter carriage driving mechanism 8' to forward the cutter carriage 7' toward the cutting burr 4, whereby the cutting burr 4' of the slab 2' placed on the roller table 6' is cut off by the knife 11a' of the cutter 11'.
Since in the above-mentioned prior art, the cutting burr 4' is substantially completely removed by a single movement of the cutter 11', it is suitable for removing a cutting burr shorter than the total length of the knife 11a' of the cutter 11' such as a cutting burr produced when fusion-cutting the slab in the width direction thereof and sticking to the lower surface thereof, but the prior art is not applicable to removal of a cutting burr longer than the total length of the knife 11a' of the cutter 11' such as a cutting burr produced when fusion-cutting the slab in the longitudinal direction thereof and sticking to the lower surface thereof.
Under such circumstances, there is a strong demand for developing a method and an apparatus which enable to remove at a high efficiency a cutting burr which is produced when longitudinally fusion-cutting a slab and sticks to the lower surface of the slab along the fusion-cutting line, but such a method and an apparatus have not as yet been proposed.